misc: Remove unused Error variables

There's a few cases which we're passing an Error pointer to a function
only to discard it immediately afterwards without checking it. In
these cases we can simply remove the variable and pass NULL instead.

Signed-off-by: Alberto Garcia <berto@igalia.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-id: 20170829120836.16091-1-berto@igalia.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

block/qcow.c

@@ -454,13 +454,11 @@ static uint64_t get_cluster_offset(BlockDriverState *bs,
                     start_sect = (offset & ~(s->cluster_size - 1)) >> 9;
                     for(i = 0; i < s->cluster_sectors; i++) {
                         if (i < n_start || i >= n_end) {
-                            Error *err = NULL;
                             memset(s->cluster_data, 0x00, 512);
                             if (qcrypto_block_encrypt(s->crypto, start_sect + i,
                                                       s->cluster_data,
                                                       BDRV_SECTOR_SIZE,
-                                                      &err) < 0) {
-                                error_free(err);
+                                                      NULL) < 0) {
                                 errno = EIO;
                                 return -1;
                             }
@@ -572,7 +570,6 @@ static coroutine_fn int qcow_co_readv(BlockDriverState *bs, int64_t sector_num,
     QEMUIOVector hd_qiov;
     uint8_t *buf;
     void *orig_buf;
-    Error *err = NULL;
 
     if (qiov->niov > 1) {
         buf = orig_buf = qemu_try_blockalign(bs, qiov->size);
@@ -637,7 +634,7 @@ static coroutine_fn int qcow_co_readv(BlockDriverState *bs, int64_t sector_num,
             if (bs->encrypted) {
                 assert(s->crypto);
                 if (qcrypto_block_decrypt(s->crypto, sector_num, buf,
-                                          n * BDRV_SECTOR_SIZE, &err) < 0) {
+                                          n * BDRV_SECTOR_SIZE, NULL) < 0) {
                     goto fail;
                 }
             }
@@ -660,7 +657,6 @@ done:
     return ret;
 
 fail:
-    error_free(err);
     ret = -EIO;
     goto done;
 }
@@ -709,11 +705,9 @@ static coroutine_fn int qcow_co_writev(BlockDriverState *bs, int64_t sector_num,
             break;
         }
         if (bs->encrypted) {
-            Error *err = NULL;
             assert(s->crypto);
             if (qcrypto_block_encrypt(s->crypto, sector_num, buf,
-                                      n * BDRV_SECTOR_SIZE, &err) < 0) {
-                error_free(err);
+                                      n * BDRV_SECTOR_SIZE, NULL) < 0) {
                 ret = -EIO;
                 break;
             }

block/qcow2.c

@@ -1820,15 +1820,13 @@ static coroutine_fn int qcow2_co_preadv(BlockDriverState *bs, uint64_t offset,
                 assert(s->crypto);
                 assert((offset & (BDRV_SECTOR_SIZE - 1)) == 0);
                 assert((cur_bytes & (BDRV_SECTOR_SIZE - 1)) == 0);
-                Error *err = NULL;
                 if (qcrypto_block_decrypt(s->crypto,
                                           (s->crypt_physical_offset ?
                                            cluster_offset + offset_in_cluster :
                                            offset) >> BDRV_SECTOR_BITS,
                                           cluster_data,
                                           cur_bytes,
-                                          &err) < 0) {
-                    error_free(err);
+                                          NULL) < 0) {
                     ret = -EIO;
                     goto fail;
                 }
@@ -1942,7 +1940,6 @@ static coroutine_fn int qcow2_co_pwritev(BlockDriverState *bs, uint64_t offset,
         qemu_iovec_concat(&hd_qiov, qiov, bytes_done, cur_bytes);
 
         if (bs->encrypted) {
-            Error *err = NULL;
             assert(s->crypto);
             if (!cluster_data) {
                 cluster_data = qemu_try_blockalign(bs->file->bs,
@@ -1963,8 +1960,7 @@ static coroutine_fn int qcow2_co_pwritev(BlockDriverState *bs, uint64_t offset,
                                        cluster_offset + offset_in_cluster :
                                        offset) >> BDRV_SECTOR_BITS,
                                       cluster_data,
-                                      cur_bytes, &err) < 0) {
-                error_free(err);
+                                      cur_bytes, NULL) < 0) {
                 ret = -EIO;
                 goto fail;
             }

dump.c

@@ -1695,10 +1695,8 @@ static void dump_process(DumpState *s, Error **errp)
 
 static void *dump_thread(void *data)
 {
-    Error *err = NULL;
     DumpState *s = (DumpState *)data;
-    dump_process(s, &err);
-    error_free(err);
+    dump_process(s, NULL);
     return NULL;
 }